Walk behind two stage snowthrowers are well known in the snow removal art. They are called “two stage” because they utilize two powered snow removal elements, namely a snow gathering auger and a snow throwing impeller. The auger extends transversely in an auger housing at the front of the snowthrower. The auger gathers snow on the ground and feeds the snow inwardly to a generally centrally located impeller behind the auger. The impeller rotates at a higher speed than the auger, accepts the snow fed to it by the auger, and throws that snow upwardly in a snow stream through an upright snow directing chute.
The auger housing typically includes an arcuate rear wall having forwardly extending side plates. The auger comprises left and right auger flights secured to an auger shaft. The auger shaft is rotatably journalled between the side plates of the auger housing. The auger flights are shaped so that each auger flight gathers snow from the ground and feeds that snow inwardly towards the center of the auger housing. In other words, one auger flight moves snow inwardly in one direction towards the center of the auger housing while the other auger flight moves snow inwardly towards the center of the auger housing in the opposite direction, i.e. one flight feeds to the left while the other flight feeds to the right.
The impeller is located in a generally cylindrical impeller housing positioned behind the auger housing. The impeller housing and impeller are arranged perpendicularly to the auger housing and the auger. In other words, the auger housing extends transversely on the snowthrower and the auger rotates about a lateral rotational axis. In contrast, the cylindrical impeller housing extends longitudinally on the snowthrower and the impeller rotates about a longitudinal rotational axis.
When looking at the auger housing and impeller housing in a front elevational view, the inlet to the impeller housing from the auger housing is a generally circular opening in the arcuate rear wall of the auger housing. This circular opening corresponds in diameter to the nominal diameter of the impeller housing. Thus, snow gathered by the auger is fed inwardly from each side by the opposed auger flights of the auger until it is pushed through the circular opening forming the inlet into the impeller housing. There, the snow is picked up and thrown as a snow stream by the impeller.
The snow stream is thrown by the impeller through a generally vertical snow discharge pipe having its lower end connected to the impeller housing. The upper end of the snow discharge pipe connects to an upright chute. The chute is rotatable from side to side on the snow discharge pipe. The purpose in rotating the chute is to selectively direct where the snow stream is thrown relative to the snowthrower, i.e. to the front of the snowthrower, to the left of the snowthrower, to the right of the snow-thrower, etc.
The snow discharge pipe is connected to the top of the impeller housing to receive and accept the snow stream being thrown by the impeller. The intersection of the snow discharge pipe and the top of the impeller housing forms an elliptically shaped opening where the circular cross-section of the lower end of the pipe intersects with the top of the cylindrical impeller housing. Generally, the snow discharge pipe is not centered on the impeller housing, but is offset on the impeller housing as shown in FIG. 9.
In most prior art snowthrowers, the distance between the top of the snow discharge pipe and the top of the impeller is quite short, usually only two or three inches. Further, in typical two stage snowthrowers, the snow discharge pipe is straight sided. In other words, the walls of the snow discharge pipe are generally vertical. In certain circumstances, snow being thrown by the impeller clogs or plugs in the snow discharge pipe. A rather solid plug can form comprising almost a solid piece of ice.
In known two stage snowthrowers of this type, it is quite difficult to remove such a plug. There is insufficient room between the plug and the impeller for the plug to fall out as a single piece. Usually, the user has to shut off the engine and come around from behind the handle assembly to where the chute is located. The user then typically uses some type of tool, such as a stick or the like, and sticks such tool down the chute to break the plug into smaller pieces and to push such pieces down through the impeller.
The need to break up and remove plugs in this manner is annoying and inconvenient. The snowthrower obviously can't be operated until the plug is removed, but doing so takes some time and effort. Under certain snow conditions, such as when throwing wet and heavy snow, plugs tend to form frequently. This requires frequent stoppages of the snowthrower and frequent plug clearing operations.